Conventionally, incandescent lamps, fluorescent lights, or mercury lamps are used as an outdoor lighting device installed along streets or in parks etc. However, these types of lighting device consume a great amount of electric power; therefore, an environmentally friendly energy saving lighting device has been sought after in recent years.
To address this, an outdoor lighting device has been proposed in which a plurality of white light-emitting diodes are arranged, which consume much less electric power. In this type of the outdoor lighting device, for example, white light-emitting diodes are disposed on a light-source-mounting surface having a staircase pattern in order to scatter light emitted from the white light-emitting diodes from front to back and from one side to the other side. This type of the outdoor lighting device distributes light uniformly to an area to be lighted by adjusting distances between a road surface and the staircase pattern by means of different heights of stairs (for example, see Patent Document 1).
Also, another lighting device is configured to use a light-emitting diode as a light source and use a light emission lens, which is disposed at a position opposed to the light source. The light emission lens has an incident-side-refraction area and an incident-side-total-reflection area on an incidence surface facing the light source, and the light emission lens has a scattering-side-light-collecting area and a scattering-side-total-reflection area on a light-diverging surface facing the light source. This type of the lighting device uses light very effectively since, when light is emitted from the light source, the light emission lens scatters the emitted light. (For example, see Patent Document 2)